ASHINGTON, Feb. 16 - It was no accident that PBS found itself turning to Elmo, the popular "Sesame Street" character, to lobby on Capitol Hill this week. There were not many options.

Public television is suffering from an identity crisis, executives inside the Public Broadcasting Service and outsiders say, and it goes far deeper than the announcement by Pat Mitchell that she would step down next year as the beleaguered network's president.

Some public television executives said that running PBS was a thankless job, and that managing a far-flung network composed of independent fiefs around the country was a particularly daunting assignment. They also said they were facing larger issues that would challenge any executive, like increased competition from the cable industry.

Corporate underwriters have been less willing to finance PBS programs, which has left the network increasingly dependent on Washington, where Republicans criticize its programming as elitist and liberal.

The network has also struggled to develop popular new shows.

"The biggest problem we've got is the structure we've got," Alberto Ibarguen, the chairman of PBS and the publisher of The Miami Herald, said in an interview yesterday. "It assumes a lot of government funding, continuing heavy levels of corporate image advertising and no competition. But in the world we're in - the world of increased cable competition, less and less government funding and cutbacks in corporate image advertising - it's a significant problem if that's your business model."

Mr. Ibarguen added: "The risk is the tighter your budgets get, the less you can afford to fail. If you can't afford to fail, you can't afford to take risks."

Among the challenges that Ms. Mitchell has confronted is a trend, lasting nearly a decade, in which corporations have scaled back on the so-called "image advertising" through which they had once financed programs like "Masterpiece Theater." According to PBS's financial statements, revenues drawn from program underwriting - which are paid directly to producers, but catalogued by PBS - reached a five-year peak of $221.9 million in 2001, dropped to $179.4 million in 2003, and rebounded slightly to $184.3 million last year.

PBS hopes to relieve some of the pressure by creating a huge endowment from the proceeds of reselling the spectrum used by its stations when they trade their current broadcast positions for new high-definition stations later in the decade. But that will take persuading the same Congressional and administration officials who have objected to its programming.

Conservatives have complained about Bill Moyers's news program (he has since retired from it) and about a recent children's program featuring a rabbit named Buster who visited a pair of lesbian parents.

After Education Secretary Margaret Spellings threatened to retract financing for that program - a controversy that some called Bustergate - Ms. Mitchell decided not to distribute it.

In an interview on Wednesday, Ms. Mitchell, 62, said she had felt no pressure, either from inside her board or outside of PBS, to step aside.

She also said she had not been personally pressured to change programming by Republicans at the Corporation for Public Broadcasting, which provides federal money to the system. But she said her programmers had worked with their counterparts at the corporation, which is led by White House appointees, in developing several new shows, including a talk show for the conservative commentator Tucker Carlson.

"They certainly want to make sure we are providing a balanced schedule," she said. "We believe we are. We check that with the people we report to - our member stations and the American public."

One high-level executive at PBS headquarters in Washington, who declined to be identified because of the sensitivity of the situation for PBS, said new managers at the Corporation for Public Broadcasting had been concerned about a perceived liberal bias at PBS as well as difficulties in fund-raising.

"The thing to remember with public broadcasting is that everything is steered by the money," the executive said. "What used to be a unique thing is now in this competitive environment and has to do whatever it can to survive, which means bending in a way it used to never bend."

Now that 85 percent of Americans subscribe to cable or satellite television, PBS's children shows, historical dramas and wildlife documentaries face competitors like the History Channel, Discovery, A & E, the National Geographic Channel, BBC America, Nickelodeon, and The Learning Channel. PBS has responded by forging new alliances, like a recent agreement to show HBO films.

Ms. Mitchell, who was interviewed between lobbying meetings, said she would devote the rest of her tenure to raising money. Officials at PBS and its affiliated stations are beginning to lobby for a share of the windfall the federal government may get later this decade when public television stations and other over-the-air broadcasters stop using the airwaves to transmit analog signals, relying instead on digital signals over cable and satellite systems.

Once the broadcasters' part of the spectrum is open, the federal government stands to collect tens of billions of dollars by reselling it to other users like wireless broadband companies. Lobbyists for public television stations are supporting legislation that would put some of the money in a trust fund for public television.

Senator Christopher J. Dodd, a Connecticut Democrat sponsoring the legislation along with Senator Olympia J. Snowe, Republican of Maine, has called for the trust fund to be administered by an independent agency following the sort of procedures used by the National Science Foundation and the National Institutes of Health.

Some critics, like Tim Graham of the Media Research Center, a conservative watchdog group, are reluctant to give PBS any independent endowment.

"They want to create an empire that does not have to answer to the Congress or the people," Mr. Graham said. "Conservatives do not want to give more tax dollars to television stations that attack their ideas."

But there are some sympathetic conservatives, at least among the advisers on the Digital Future Initiative committee created by Ms. Mitchell, which met Wednesday in Washington to contemplate how PBS could put a trust fund to use. Norman Orenstein, a committee member who also sits on the PBS board, said Republicans on the committee believed that a trust fund could pay for socially useful programming.

"We're focusing on education and children and making the case that public broadcasting can do valuable things in a digital age that no one else can or will do," said Mr. Orenstein, a fellow at the American Enterprise Institute, a conservative research group.

Referring to the recent programming incident, he said, "The timing couldn't have been worse on the Buster thing. This is not a time you want to be in the cross hairs."

PBS is also being criticized by others, like Jeffrey Chester, the executive director of the Center for Digital Democracy and a longtime advocate of more money for public television.

"I'm concerned that PBS is so desperate for funding and support from the Republican-dominated Congress that they're willing to sell their legacy," Mr. Chester said. "They could forgo their historic mandate to do cutting-edge programming and replace it with Bush-administration-friendly educational content."

John Tierney reported from Washington for this article, and Jacques Steinberg from New York.